Effects of Manure-Based Nitrogen Substitution for Chemical Nitrogen Fertilizers on Economic Benefits and Water-Use Efficiency of Maize

How to use nitrogen fertilizer is crucial for farmers in boosting crop yield and fostering sustainable agricultural development. We hypothesized that replacing the nitrogen (N) provided by mineral fertilizer with manure would enhance the soil water storage, increase water use efficiency (WUE), maintain maize yield, and improve economic benefits. We performed the experiment by replacing 0% (CK), 25% (M25), 50% (M50), 75% (M75), and 100% (M100) of mineral N fertilizer (225 kg ha–1) with an equivalent amount of N from manure during 2016–2019. M25 and M50 increased the soil water storage at 0–2 m depth after maize harvest, while M25 significantly decreased the evapotranspiration by 5.27–22.14% compared with CK. The replacement treatments significantly increased maize yield and WUE by 6.58–13.62% and 5.68–18.00%, respectively, during the fourth fertilization year. Meanwhile, the net benefits of the replacement treatments were significantly higher than that of CK in the year of higher precipitation and irrigation water. M75 significantly increased net benefits by 8.47–35.51% compared with CK. M75 had the highest comprehensive evaluation score. Thus, the study proposes a combination of 75% N from manure with 25% N from mineral fertilizer to achieve a high maize yield and benefits.